I have no experience with the Mesa Stock but I hunt with an 870 using a Choate Mk5 stock. I really like having the pistol grip stock, but I wouldn't want to shoot a 12-ga pistol grip only.
A gunfight is not the time to learn new skills.
If you ever have a real need for more than a couple of magazines, your problem is not a shortage of magazines. It's a shortage of people on your side of the argument. -- Art Eatman